My newly arrived Tamron 17-50 2.8 back focus with sony a57... mY sigma 75-200 2.8-3.5 backfocus too... I didn´t notice that with kit lens but that is probably because the deeper dof covers it... by f4 or f4.5 its hard to tell if you are backfocusing in normal range lenses...

It would be wise to give the feature to clients so that they don´t trade for Sony NIkon or Olympus (I had olympus e-pl1 and CDAF always nails focus!

There are reports of opening the sony a57 near and moving with a screw like mechanism the autofocus calibration. Did anyone made it work?